World and levels › Water and roads
Water in the world: lakes, rivers and shores
Know first: Landscape: terrain from a heightmap, What real land looks like
Water in a game is not a liquid. It is a surface with a material, laid over a pit in the ground. This lesson explains why the level of a lake is always flat and why the ground, not the outline of the water, draws the shape of the lake. It covers why a river is a ribbon that can only go downhill, and how a flow map steers the ripples around its bends. You will learn why depth turns blue and dark, where the foam at the edge comes from, why a gentle shore flickers and what shows on the bottom. The last part shows how water cuts its own bed into the ground with a layer of edits, in Unreal and in other engines. This is the twelfth lesson of the course “Your own open world.”
Why this matters
A beginner puts a plane of water into the world. An hour later the result looks like this:
- the lake hangs in the air at one edge: from the side you see a thin shelf of water above the slope;
- on the other side the same water sticks out of a hill;
- halfway along, the river climbs a hill and flows on as if nothing had happened;
- the ripples on the river crawl in one direction and in a bend go across the bank;
- the water is one blue everywhere, at the shore and in the middle, like blue glass;
- a trembling, jagged edge runs along a gentle beach;
- where the river flows into the lake, a seam shows as a straight line.
All of these have one cause: the beginner pictures a liquid, and a game has none. There is a surface, a material and a few simple rules: the level is flat, a river goes down, and the color depends on the thickness of the water. The lesson “How a world is built: from large to small” places water in the general order of work: on the second pass, together with the shape of the ground. The lesson on landforms explains why a lake can exist only in a bowl and how water shapes valleys. This lesson is about laying that water into the world so that players believe it.